1. Field of The Invention
The invention relates to contacts for use with SIMM sockets, particular to stamped contacts within a slanted SIMM socket which should keep a low profile and minimum space on a PC board on which the SIMM is mounted.
2. The Prior Art
SIMMs (Single In-line Memory Modules) are popularly used in the recent computer industry, and therefore the SIMM sockets are also commonly designed for receiving such SIMMs therein for signal transmission between such modules and the PC board on which such sockets are mounted. The contacts for use within the SIMM sockets can vary in different ways as shown in U.S. Nos. 4,737,120, 4,984,996, 4,998,890, 5,013,257, 5,015,194, 5,041,005, 5,061,200, 5,064,381, 5,076,804, 5,080,602, 5,085,593, 5,100,337, 5,116,237 and 5,199,895.
As well known, the dimension of the computer set becomes tinier and tinier, and it means that the lay-out (i.e., the horizontal dimension), and the height (i.e., the vertical dimension) of the socket should keep as minimum as possible in the design. To minimize the horizontal and vertical dimensions of the socket, the width and the height of the socket are reduced and thus the inside corresponding cavity for receiving the contact is substantially smaller than that in the previous regular one. That is to say that the space for the contact beam(s) design is getting more and more critical to have a minimum normal force thereof with regard to the corresponding inserted module under such a small dimension. Furthermore, to minimize the vertical dimension of the whole assembly (including the module and the socket) as the module is received within the socket, the slanted type SIMM sockets are popularly used for allowing the inserted module lying slopingly therein. The slanted type SIMM socket can be referred to U.S. Pat. Nos. 5,013,157, 5,041,005, 5,064,381, 5,085,593, 5,100,337, 5,116,237 and 5,174,780. In the fact, to reduce the height to a maximum limit, the angle of the slanted type SIMM socket with regard to the PC board on which the socket is mounted, is designedly arranged to be smaller than before, for example, the angle being from 40.degree. C. as shown in aforementioned U.S. Pat. No. 5,366,390 to 22.5.degree. C. described in the present invention.
As noted, the SIMM socket is design to have the module inserted in a first position for the zero insertion force, and further rotated in a second position for the required normal force. The tinier and/or more slanted the socket is, the tougher such electrical and mechanical connection applications of the module in the socket are. This is because several limitations should be applied thereto. As shown in FIGS. 1 and 1(A), the stamped contact 10 in the cavity 11 of the slanted SIMM socket 12 generally includes a pair of contact beams 13, 14 (i.e., the high beam and the low beam) for sandwiching the module 17 therebetween wherein the high beam 13 engages the pads 15 on the top surface 16 of the inserted module 17, and the low beam 14 engages the pads 18 on the undersurface 19 of the module 17. First, the distance S between the contact apexes 20, 21 of the contact beams 13, 14 should be sufficiently large, at least beyond the thickness of the module 17, for allowing zero insertion force of the module in the slot 22 of the socket 12 (i.e., the first position), but also be sufficiently small for allowing the minimum required normal force occurring when the module 17 is successively rotated to mechanically and electrically engage the corresponding pair of contact beams 13, 14 (i.e., in the second position). Basically, it is uneasy to achieve this issue in a tiny slanted SIMM socket.
Secondly, the contact apexes 20, 21 of the contact beams 13, 14 tend to substantially move in opposite directions with each other when the module is rotated from the first position to the second position. Such opposite movements includes the opposite movements along the surfaces of the module 17 in the directions from the top (bottom) edge of the module to the bottom (top) edge of the module. In other words, as shown in FIG. I(A), the contact apex 20 of the high beam 13 moves to the bottom edge of the module in the direction A, but the contact apex 21 of the low beam 14 moves to the top edge of the module in the direction B. Obviously, such opposite movements almost have the corresponding contact apexes 20, 21 located outside of the electrical pads 15, 18 on the module 17, i.e., the contact apex 20 of the high beam 13 being located adjacent the lower edge of the pad 15 on the top surface 16 of the module 17 and the contact apex 21 of the low beam 14 being located adjacent the upper edge of the pad 18 on the undersurface 19 of the module 17, even though such apex 15, 18 are generally facing the center portion of the corresponding pads 20, 21 when the module 17 is in the first position. Such bad positioning of the contact apexes 20, 21 to the pads 15, 18, will result in poor mechanical and electrical engagement of the contact 10 with the module 17, and the unexpected intermittence in data communication thereof. Using a big head type contact apex for not dropping out of the corresponding pad may resolve this problem, but it will decrease the required minimum distance S between the contact apexes 20, 21 and substantially jeopardize the normal insertion force arrangement. Differently, changing the shape of the contact beam to reduce the deflection of the contact beam and have the contact apex be in a smaller displacement for not dropping out of the corresponding pad, may solve this problem, too, but it will also jeopardize the minimum required normal force which is originally designed for engagement between the module and the contact apexes.
Therefore, an object of the invention is to provide specifically configured contacts for use with a slanted SIMM socket, wherein the contact apexes of the contact beams can not only provide a sufficient space therebetween to permit zero insertion force of the module, but also be located as much within the range of the corresponding pad as possible to achieve a reliable good electrical data transmission between the module and the socket.